Proteins and DNA are information rich molecules with structural and electrical properties which make their incorporation into the human manufacturing arsenal an attractive proposition. Several microstructures using oligonucleotides as building blocs have been demonstrated (N. C. Seeman, Ann. Rev. Biophys. Biomol. Struc., vol. 27, pp. 225, 1998; B. Winfree, F. Liu, L. Wenzler, and N. C. Seeman, Nature, vol. 394, pp. 539, 1998.), and many particles/objects have been derivatized with DNA strands or oligonucleotides (R. Bashir, “DNA-Mediated Artificial Nano-Bio-Structures: State of the Art Future Directions,” Superlattice and Microstructures, vol. 29, pp. 1-16, 2001.) Short strands of DNA, also known as aptamers have been suggested as a tool in DNA mediated self assembly of micro components into larger subassemblies or onto a PC board (C. F. Edman, C. Gurtner, R. E. Formosa, J. J. Coleman, and M. J. Heller, “Electric-Field-Directed Pick-and-Place Assembly,” HDI, vol. October, pp. 30-35, 2000; C. F. Edman, R. B. Swint, C. Gurtner, R. B. Formosa, S. D. Roh, K. B. Lee, P. D. Swanson, D. B. Ackley, J. J. Coleman, and M. J. Heller, “Electric Field Directed Assembly of an InGaAs LED onto Silicon Circuitry,” IEEE Photonics Tech. Lett., vol. 12, pp. 1198-1200, 2000; C. A. Mirkin, R. L. Letsinger, R. C. Mucic, and J. J. Storhoff, Nature, vol. 382, pp. 607, 1996.). Proteins have also been used in a wide variety of microstructures with motor proteins, perhaps the most studied example. The first examples of combinations of proteins with micromachined structures were realized recently.
The combination of the natural biopolymers with microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS) promises the advent of a totally new class of sensors and actuators with applications in drug delivery, diagnostics, biocompatible surfaces, prosthetics and many other fields.
Advanced biomaterials are of high importance in biomedicine, and especially, in new-generation medical devices and implants. These materials can be used in a multitude of biomedical applications related to the treatment and management of disease. Currently, there are a limited number of biomaterials that are suitable for biomedical applications. For example, the materials need to be prepared and perform in a reproducible, accurate, selective, and sensitive manner, and they need to be amenable to integration into devices that can be employed in a variety of applications (e.g., biosensors, delivery systems, diagnostic and high throughput screening platforms, etc.), those being in vitro or in vivo.
Conventional drug delivery methods incorporate tablets, capsules, and emulsions that have difficult-to-control release rates and nonspecific delivery sites. An ideal drug delivery system would be able to provide a specific release profile in response to an external stimulus. Traditional drug release tablets cannot control the amount of drug released efficiently. The drug concentration may extend beyond the therapeutic window risking ineffectiveness or toxicity. Over the last two decades a new type of drug delivery, controlled drug delivery (also referred to as controlled release), has evolved in order to optimize drug therapy when conventional drug delivery methods, such as tablets, pills, solutions, and suspensions, are inadequate. Controlled release is most commonly achieved by incorporating (or “encapsulating”) drugs in either biodegradable or nondegradable polymers, which can control the release of the drug to the body over specific times ranging from a day to several years. A major limitation in the usefulness of controlled release systems is that conventional implantable devices release drugs at a predetermined rate(s). However, in certain instances, it is required that drugs are administered either at a life-threatening moment or repeatedly at a certain critical time of day. The latter is a requirement in the design of controlled release systems for certain disease states, such as diabetes, heart disease, and hormonal disorders. Drug delivery technology could be brought to the next level if we could understand how to prepare “intelligent” polymers that are “responsive” to the patient's therapeutic requirements and deliver certain amount of a drug in response to a biological stimulus.
A multitude of binding proteins exist for a variety of ligands such as sugars, amino acids, peptides, and inorganic ions. Likewise, enzymes are another class of proteins that undergo conformational changes as they catalyze a specific reaction. Enzymes can serve as biorecognition elements for substrates, inhibitors, and allosteric effectors. These binding proteins and enzymes come from a range of organisms, some of which grow under extreme environmental conditions. These organisms, termed extremophiles, have adapted to prosper at temperatures as high as that of boiling water in thermal vents (hyperthermophiles) or as low as that of icebergs (psychrophiles). Unlike conventional of-the-shelf proteins that come from organisms that grow at 20 to 37° C., and are non-functional at temperatures above or below this range, proteins from extremophiles can perform under severe conditions.
There are a few examples in the literature where proteins have been integrated into materials capable of displaying a significant change in their characteristics in response to a stimulus. Most of these examples refer to the development of what are known as “smart” polymers or devices intended for use in delivery systems. The “smart” polymers can be prepared so that they are responsive to the individual patient's therapeutic requirements and deliver certain amount of a drug in response to a biological stimulus.
The conventional “smart” polymer based on antigen-antibody interactions showed promise for responsive drug delivery. A semi-interpenetrating hydrogel polymer network was prepared consisting of a polymer containing rabbit antibody (IgG) and goat anti-rabbit IgG as the antigen. This hydrogel is able to swell in the presence of free antigen, rabbit IgG, due to competition between free antigen and polymer-immobilized antigen. Upon removal of free antigen, the hydrogel shrinks, thus, exhibiting a reversible swelling and shrinking behavior, which was dependent on free antigen concentration.
There is a need for high-throughput screening devices in the pharmaceutical industry for rapid and accurate selection of possible drug candidates that are most active or effective. Currently, laborious combinatorial techniques are used to screen analytes. These techniques are taxing on both time and resources. Utilizing a stimuli-responsive hydrogel array of microdomes of the present invention, allows for efficient screening of these compounds in minutes.
This invention is directed to a highly sensitive responsive system for detecting analytes based on the induced conformational change upon binding of the analytes to their respective binding proteins. The system can also be useful as an actuator or biosensor. The conventional hydrogel synthesis does not permit exact control of three-dimensional structure of the hydrogel microdome, making it difficult to predict hydrogel performance and hindering the potential for biomedical applications. To overcome this problem, this invention includes the preparation of a hybrid hydrogel that incorporates a biopolymer within its structure. The biopolymer can be a monomer or multimer. This hybrid hydrogel has precise and reproducible swelling characteristics.